Screw jack



H. J. SCHMICK. 7

SCREW JACK.

APPLICATION FILED MAY 10, I921.

Patented Nov. 28, 1922.

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' H. J. SCHMICK.

SCREW JACK.

APPLICATION FILED MAYIO, 1921.

Patented Nov. 28, 1922.

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r \IT HENRY J. SCHMICK, OF WILLIAMSPORT, PENNSYLVANIA, ASSIGNOR TOSOHMICK SCREW AND GEAR COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

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Application filed May 10, 1921. Serial-No. 468,256.

To all whom it may concern:

Be it known that HENRY J SQHMIGK, a citizen of the United States, residing at Williamsport, county of Lycoming, State of Pennsylvania, has invented an improvement in Screw Jacks, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawingsrepresenting like parts.

This application is a continuation in part of applicants prior applications filed November 12, 1920, Serial No. 423,693 and Serial No. 123,694,. for improvements in screw jacks and lifting jacks, respectively.

This invention aims to improve and simplify the construction, increase the durability, and lessen the manufacturing cost of portable jacks, particularly such as are used for automobiles, although it is not restricted to such ,jacks.

The invention further aims to promote rapidity and ease of operation, and to protect the operating parts from dirt and keep them lubricated ready for use at all times.

The jack shown in the drawings is an illustrative embodiment of the invention and illustrates a preferred means of attaining its objects.

In the drawings, Fig. 1 is aside elevation of/a screw jack showing the top section or casing in partly raised position;

Fig. 2 is a cross-section of the same on the line 22 in Fig. 1;

Fig. 3 is a vertical central section of the jack showing the operating gears,-ratchet and screw in side elevation; U

Fig. 4 is a sectional view of the top part of the jack; drawn to a larger scale, showing the construction of the ratchet and friction device for holding the jack in raised position under load; and Fig. 5 is a perspective view of the hollow base member.

, Referring to Figs. 1 and 2, the jack shown therein has a base 11 supporting a hollow pillar or body 12 upon which the top or casing section 13 is arranged to slide up The body has two arms or lengthwise guides 14 formed upon its exterior, and the casing 13 has corresponding grooves 15 fitting the guides. The inner and outer surfaces of the body and casing are left rough except for these guides and grooves, which are machined to slide easily and malntain coaxial .and angular alinement of the parts in all positions of the jack.

Referring more particularly to Fig. 3, the hollow body 12 has a series of partial screw threads 16 cast on each half of its inner surface to receive the jack screw 17.

These series of threads extend from top to bottom of the bodyand the spaces between their ends form two diametrically opposed grooves likewise extending from top to botits being removed and folded up. The handle alsoaflords convenient means for carrymg the jack and for ositioning it under the axle of an automobi e or other thing to be lifted.

Referring more particularly to Fig. 4, a combined friction and thrust plate 23 isv arranged to turn on the to end of the stem.18 of the screw. This p ate is adapted on its upper side to engage against the under side of the top part 24 of the casing. The plate 23 has a central hub 25 which projects into a circular recess in the under side of the top 24 in line with the axis of the screw. The .hub is hollow to receive the upper end of the stem 18. .The hub 25 has a solid top end, and contains a thrust ball '26 against which the upper end of the screw stem 18 bears, thereby providing an effective anti-friction bearing not easily I and screw.

The plate 23 is left rough except for the hub and the top surface, which are machined to fit the under side of the top 24 of the easing, which is also machined at. the places where the plate touches it.

A cover 31 is secured to the top over the opening for the gear 19 .anda cover 32 .having a bearing for the shaft carrying the operating gear 20 is also secured tothe top. The covers may be removed to give access to the gearing and ratchet, and for adding grease to them.

The top part 24 of the casing is formed. with a central post or support 33 and a step 34 at one side of .the post for engaging under the article. to be lifted. A removable extension post 35 is also provided for lengthening the jack-in case 'of need.

To operate the jack the handle 22 is rotated to raiseor lower the screw 17 in the body 12. If the screw is turned to raise the body the ratchet slides over the teeth on the plate 23, and permits free rotation.

If the screw is turned to lower the body the ratchet will engage in the ratchet teeth and tum the plate against whatever friction may be occasioned by the load. The resistance to turning is greater with larger loads, thereby preventing the screw from being forced down by the load. 1

The construction of the casing and operating parts of the jack is simple and strong, the design being such that cast iron may be used for all of the principal parts and very little machine work 1s required to finish them. The working parts are all encased and adequate provision is. made for insurlng proper lubrication of the thread The invention is not restricted to the details of construction shown and described. I claim the following as my invention:

1. A screw j ack comprising a casing having its interior threaded from end to end, a screw of coarse pitch enga 'ng said thread, said screw having a short tli at itslower end of large diameter and a long stem projecting from said casing, means on said casing for iding said stem and means carried by said stem for rotating said screw. 1

2. A screw -jack provided with a sore having a short threaded portion of large diameter and a long stem, a barrel nut constituting the body of said jack and enclosing said screw and stem, means slidahle on--the exterior ,of said barrel nut for guiding the extremity of said stem, a bearing sleeve carried by said guiding means, a, thrust bearing between said sleeve and .stem, and means carried by the stem for rotating said screw.

3 A screw jack comprising an enclosing casing having an open end, a hollow cylinder 05 within said casingwith one end projecting readed portion from said open end, said casing and cylinder being arranged to telescope, the inner walls of said cylinder having partial screw threads and a screw arranged in the cylinder and engaging said threads, whereby a communication is provided for between the spaces within said cylinder on either side of said screw, said screw having a swivel connection withsaid casing, and means in said casing for operating said screw, said operating means being entirely encased whereby dirt is prevented from reaching said operating means and screw, and lubricant is retained in the cylinder'in proximity to the-operating parts.

4:. In a screw operated jack, a screw having'a stem, a barrel nut enclosing the screw and major part of the stem and having 1nterrupted threads, said barrel nut having a closed base, a casing swiveled to said stem and enclosing said nut, the space within said I terrupted threads, said barrel nut having a closed base, a casing swiveled to said stem and enclosing and sliding on said nut, the space Within said casing and nut being adapted to contain lubricant, spaces between the ends of-said threads for permitting lubricant to circulate, and a'ctuatingmeans for said screw housed within said casing.

' 6. A screw jack having a screw with an angle of lead greater than the angle of redirection to operate said jack, and riction in a 1 pose of thethread, a casing for said screw, means for rotating sald screw freel means between said screw and casingfi'ective in'proportion to the load on said jack to prevent rotation of said screw in the reverse direction, said friction means having a ratdhet connection with said rotating means, and a pawl unit for said ratchet C011? nection comprising a cup, a detent slidable.

therein, and a sprmg in said cup bearing against said detent.-

'7. A screw jack comprising an enclosing casing having an open end, ahollow cylinder within said casing with one end projecting from said open end, said casing and cylinder bei arranged to telescope, the inner walls 0 said cylinder having screw threads and a screw arranged in the cylinder,

and engaging said threads, said screw hav- "ing astem projecting from the inner end of said cylinder and, jou'rnalled atits extremity in-said enclosing casing, a shoulder near the extremity'of said stem, and a friction memberhaving a bearing against said shoulder, said frlction member bearing against and having frictional engagement with said casmg, and means within said cas iasaeee ing operatively connected to said stem for rotating said screw, said rotating means having a one way operating clutch connection with said friction member preventing relative rotation in one direction whereby it is frictional-11y held by said casing against operation to move said screw in said direction.

8. A screw jaclr comp-rising enclosing casing having an open end, a hollow cylinder within said casing with one end projecting from said open end, said casing and cylinder being arranged to telescope, the inner walls of said cylinder having screw threads and a screw arranged in the cylinder and engaging said threadsysaid screw having a stem projecting from the inner end of said cylinder, a friction member having a bearing against said projecting end, said friction member bearing agalnst and having frictional engagement with said casing, a ratchet on said'triction member and a pawl rotatable with said stem and engaging said ratchet, said pawl permitting free rotation of said stem with respect to said friction member in one direction, and preventing relative rotation thereof in the opposite direction. Y

9. A screw jack having an operating screw, tubular casing sections slidably arranged one within the other to enclose the screw, the inner section having an internal screw thread and external guides formed integral therewith, and the outer'section having internal guides fitting said external guides to position the sections concentrically and prevent relative rotation.

10. A screw jack having an operating screw' with a long stem, tubular casing sections slidably arranged one within the other 'to enclose the screw, the inner section haw ing an internal screw thread and external guides formed integral therewith, and the having internal guides fitting said external guides to position the sections concentrically and prevent relative rotation,

and means carried by said outer section for rotating the screw and guiding its stem.

11. A screw jack having an operating screw with a long stem, tubular casing secs tions slidably arranged one within the other to enclose the screw, the inner section having an internalscrew thread and external guides formed integral therewith, and the outer section having internal guides fitting 5 said external guides to position the sections concentrically and prevent relative rotation, and means for rotating the screw and goid ing its stem, said means comprising a device for restraining said screw against rotation e in one direction without interfering with its freedom of rotation'in the opposite direction. 7

12. A. screw jack having a screw with a stem, a thrust member having a hub en 6a;

circling said stem, the extremity of said hub being closed over. the end of said stem, and an antifriction ball bearing between the end of said stem and the extremity of said hub.

13. A screw jack having a screw with a i smm, a thrust member having a hub encircling said stem, the extremity of said huh being closed over the endof said stein, a hardened steel pin inserted at the end of said stem, and an antifriction ball bearing a between the end of said stem and the extremity of said pin. 1

14. Asa new article of manufacture, a portable screw jack having a base and tubular body supported thereby, said body having screw threadscast on its inner wall for its entire length, said screw threads bein interrupted by two diametrically oppose grooves runnm lengthwise of said body from end to en a cast metal screw having 3 a short threaded end portion and a lon stem extending out from the upper end 0 said body, a casin closed at its top andsurrounding said bo y, said body and casing having guides and grooves integral there- 9 with for maintaining said casing in axial and angular alinement with said body, a hub on said casing to receive the end of said screw, a ball thrust bearing between the end of'said screw and said hub, and means e1 garried' b said casing for rotating Said screw in either direction and for frictionally holding, it against rotation in one direction. In testimony whereof, I have" signed my name to this specification.

i HENRY J. sonnr 

